Two domains of MyoD mediate transcriptional activation of genes in repressive chromatin: A mechanism for lineage determination in myogenesis
Two domains of MyoD mediate transcriptional activation of genes in repressive chromatin: A mechanism for lineage determination in myogenesis
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DOI：
10.1101/gad.11.4.436
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发表时间：
1997-02-15
影响因子：
10.5
通讯作者：
Tapscott, SJ
中科院分区：
文献类型：
--
作者：
Gerber, AN;Klesert, TR;Tapscott, SJ
遗传学研究表明，MyoD和Myf5建立了骨骼肌谱系，而肌生成素介导了终末分化，但这种区别的分子基础尚不清楚。我们发现，MyoD可以在肌肉基因增强子的结合部位重塑染色质，并激活以前沉默的位点的转录。转化生长因子-β、碱性成纤维细胞生长因子和丁酸钠阻断了MyoD介导的染色质重组和转录的启动。相反，当在染色质重塑发生后加入转化生长因子-β和丁酸钠时，并不会阻止转录。在激活转录沉默染色质区域的基因方面，MyoD和Myf-5的效率是肌肉生成素的10倍。MyoD蛋白的缺失突变表明，激活内源基因的能力取决于两个区域：位于酸性激活结构域和bHLH域之间的富含半胱氨酸和组氨酸残基的区域，以及蛋白质羧基末端的第二个区域。这两个区域以前都没有显示过调节基因转录，而且都有在Myf5蛋白中保守的结构域。我们的结果建立了骨骼肌染色质模型的机制，并定义了独立于激活结构域的MyoD结构域，参与染色质重组。
Genetic studies have demonstrated that MyoD and Myf5 establish the skeletal muscle lineage, whereas myogenin mediates terminal differentiation, yet the molecular basis for this distinction is not understood. We show that MyoD can remodel chromatin at binding sites in muscle gene enhancers and activate transcription at previously silent loci. TGF-beta, basic-FGF, and sodium butyrate blocked MyoD-mediated chromatin reorganization and the initiation of transcription. In contrast, TGF-beta and sodium butyrate did not block transcription when added after chromatin remodeling had occurred. MyoD and Myf-5 were 10-fold more efficient than myogenin at activating genes in regions of transcriptionally silent chromatin. Deletion mutagenesis of the MyoD protein demonstrated that the ability to activate endogenous genes depended on two regions: a region rich in cysteine and histidine residues between the acidic activation domain and the bHLH domain, and a second region in the carboxyl terminus of the protein. Neither region has been shown previously to regulate gene transcription and both have domains that are conserved in the Myf5 protein. Our results establish a mechanism for chromatin modeling in the skeletal muscle lineage and define domains of MyoD, independent of the activation domain, that participate in chromatin reorganization.